1. Field
The present teachings relate to radio-frequency (RF) amplifiers used in RF circuits. More particularly, the present teachings relate to methods and systems for reducing parasitic loading, such as for example stray capacitance, in RF amplifiers used in multiband and multimode RF circuits.
2. Description of Related Art
In an effort to cover the many communication standards and frequency bands used in today's data and voice transmissions, RF circuits used in today's mobile devices are designed with multiple RF amplifiers (e.g. a power amplifier (PA)) each tailored to a specific communication standard and frequency band. During typical operation of the device (e.g. mobile handset, tablet) only one of the multiple RF amplifiers is activated (e.g. turned ON) and used for transmission of a signal, and the unused RF amplifiers are deactivated (e.g. turned OFF). A turned OFF RF amplifier can exhibit a residual loading, such as a stray capacitance, with respect to a common DC-DC power supply used to supply power to the multiple RF amplifiers. Such residual loading can affect the supply provided to a turned ON RF amplifier and thereby impact operation of the ON RF amplifier. This impact becomes even more apparent in the case where the DC-DC power supply is modulated, such as in the case of an envelope tracking amplifier.